In general, a hands-free device disposed in a vehicle is capable of allowing a user of a cellular telephone to conduct a call without having to operate the cellular telephone. For instance, when an incoming call is received via the cellular telephone, the hands-free device may output a sound/voice of the caller from a vehicle-installed speaker, and may input a sound/voice of a recipient of the call to a vehicle-installed microphone. One such device is disclosed in, for example, Japanese Patent Laid-Open No. 2000-134253.
In a situation where the cellular telephone belongs to a driver of the vehicle, the hands-free call function may be utilized by the driver for, at the very least, safety reasons. In a situation where the cellular telephone belongs to a passenger, who is not the driver, the operation of the hands-free call function may not be desired by the passenger. For instance, the passenger may want to keep the call private and may prefer not to have the driver or other passengers to know the content of the call or even the person who is calling.
Whether the cellular telephone brought into the vehicle is the driver's property or a passenger's property may be hard to determine. Therefore, it may be difficult to determine whether the hands-free call function should be established.